Background The extent to which hypertension-related excess risk of dementia can be mitigated or eradicated through lifestyle factor modification remains unclear. Objective To explore the association between lifestyle behaviors and hypertension-related excess risk of dementia. Methods In this prospective cohort study using data from the UK Biobank, participants were enrolled from 2006 to 2010 and followed up until December 2022. A healthy lifestyle score was constructed by assigning one point for each of the seven selected healthy lifestyle factors. The association of dementia risk in individuals with hypertension according to the healthy lifestyle score was compared to individuals without hypertension. Results This study included 337,378 individuals. During a median follow-up of 13.6 years, 5390 participants developed dementia. A higher healthy lifestyle score was associated with a gradual decrease in the excess risk of dementia for individuals with hypertension compared to individuals without hypertension. Excess dementia risk was not detected among individuals with hypertension who adopted at least six healthy lifestyle factors (hazard ratio (HR) = 1.05 (95% confidence interval (CI): 0.96-1.14)) for six scores; HR = 0.93 (95% CI: 0.82-1.06 for seven scores). The protective association between adhering to all seven healthy lifestyle factors and dementia was significantly stronger for individuals <60 years old than for individuals >= 60 years old. Conclusions For individuals with hypertension who adopted at least six healthy lifestyle factors had no hypertension-related excess risk of dementia.